3-cycloalkylthio-3-azabicyclo{8 3.2.2{9 nonanes as inhibitors

ABSTRACT

wherein n is from two to nine.

finite States atent Inventor John Joseph DAmico Akron, Ohio App]. No. 17,970

Filed Mar. 9, 1970 Patented Dec. 14, 1971 .Assignee Monsanto Company St. Louis, Mo.

3-CYCLOALKYLTHIO-S-AZABICYCLO[3.2.2] NONANES AS INHIBITORS 21 Claims, No Drawings U.S. Cl 260/79.5 B, 252/182, 260/79.5 B, 260/239 BA, 260/780, 260/785, 260/786, 260/793, 260/796, 260/797,

Int. Cl C08! 27/06, C07d Field of Search 260/41.5

MP, 79.5 B, 239, 780, 784, 785, 792; 252/182 [56] References Cited UNITED STATES PATENTS 3,262,927 7/1966 DAmico 260/239 3,371,074 2/1968 D'Amico 260/79.5 3,422,078 1/1969 D'Amico Zoo/79.5

Primary Examiner.ioseph L. Schofer Assistant ExaminerC. A. Henderson, Jr. Attorneys-Richard O. Zerbe, J. E. Maurer and Neal E. Willis ABSTRACT: Compounds of the formula N S Cg /(CHz)n CH2 wherein n is two to nine which are stabilizers of organic compounds and inhibitors of premature vulcanization.

3-CYCLOALKYLTIIIO-3-AZABICYCLO[ 3 .2.2 ]NONANES AS INHIBITORS SUMMARY OF THE INVENTION The sulfenamides of this invention have the formula a S NSCH CH2) where n is an integer from two to nine. They may be prepared by reacting a cycloalkylthio halide with 3-azabicyclo[3.2.2 ]nonane. Examples of suitable cycloalkyl radicals are cyclopentyl, cyclohexyl, cyclooctyl, cyclodecyl and cyclododecyl.

The new compounds inhibit premature vulcanization or scorch of vulcanizable rubber compositions and active vulcanization at curing temperatures. This means that rubber stocks containing the inhibitors cure faster yet have greater processing safety. The inhibitor activity is supported by the presence of the cycloalkyl radical. Replacement of the cycloalkyl radical with an aryl radical gives compounds with entirely different properties.

The inhibitors of my invention may be used in natural and synthetic rubbers. Synthetic rubbers that may be improved by the process of this invention include cis-4-polybutadiene, butyl rubber, ethylene-propylene terpolymer rubber, polymers of 1,3-butadiene for example 1,3-butadiene itself and of isoprene and copolymers of 1,3-butadiene with other monomers, for example styrene, acrylonitrile, isobutylene, and methyl methacrylate. The invention relates to diene rubbers, and the terms rubber and diene rubber are synonymous for the purposes of this invention.

Rubber stocks containing delayed action accelerators can be used in the process of this invention. The stocks are fully accelerated in the absence of the inhibitor and may contain an amine to protect the rubber from degradation. The amine usually reduces processing safety, but the new vulcanizing systems are effective to prevent premature vulcanization in the presence thereof. More scorchy accelerators can also be used with an excellent degree of improvement. The improved vulcanizing method of this invention can be used advantageously to process stocks containing furnace carbon blacks as well as stocks containing other types of blacks and fillers used in rubber compounding. The invention is also applicable to gum stocks.

The data infra illustrate that a combination of an accelerator and an inhibitor of this invention is an improved rubber additive which allows significantly longer and safer processing time for rubber. Further, the accelerator-inhibitor combinations of this invention may improve the modulus of a vulcanizate considerably. The storage stability of a rubber mixture containing an accelerator-inhibitor combination of this invention is improved compared to a rubber mixture containing an accelerator alone.

My invention is applicable to rubber mixes containing sulfur-vulcanizing agents, organic accelerators, and antidegradants. For the purposes of this invention, sulfur-vulcanizing agent means elemental sulfur or sulfur-containing vulcanizing agent, for example, an amine disulfide, or a polymeric polysulfide. The invention is applicable to vulcanization accelerators of various classes. For example, rubber mixes containing the aromatic thiazole accelerators which include N-cyclohexyl-2- benzothiazolesulfenamide, 2-mercaptobenzothiazole, Ntertbutyl2-benzolthiazolesulfenamide, 2-benzothiazolyl diethyldithiocarbamate, N,N-diisopropyl-Z-benzothiazolesulfenamide, and 2-(morpholinothio)benzothiazole can be used. Thiazole accelerators other than aromatic can be used. Stocks containing accelerators, for example tetramethylthiuram disulfide, tetramethylthiuram monosulfide, aldehyde amine condensation products, and guanidine derivatives, are substantially improved using the method of my invention. Stocks containing mixtures of accelerators are substantially improved by using the method of my invention. Rubber mixes containing antidegradants, for example N-1,3-dimethylbutyl-N'- phenyl-p-phenylenediamine, N,N-bis( l ,4-dimethylpentyl)-pphenylendediamine, N,N'-bis(2-octyl)-p-phenylenediamine, and other phenylenediamines, ketone, ether, and hydroxy antidegradants and mixtures thereof, are substantially improved using the process of my invention.

PREFERRED EMBODIMENTS 3-Cyclohexylthio-3-azabicyclo[3.2.2]nonane is prepared as follows:

Cyclohexyl sulfenylchloride (45.1 g., 0.25 mole) in 150 ml. of heptane is added dropwise in 15 minutes to a stirred solution of 3-azabicyclo[3.2.2]nonane (37.5 g., 0.3 mole) and triethylamine (30.4 g., 0.3 mole) in 500 ml. of ethyl ether at l 5 C. The mixture is stirred 24 hours at 2530 C. 300 ml. of water is added and the mixture stirred an additional 15 minutes. The ether-heptane layer is separated, washed with water until neutral, and dried over sodium sulfate. The ether and heptane are removed in vacuo at 90 C. at 1-2 mm. Hg. The residue is filtered hot to remove one gram of solids. 51 Grams percent yield) of an amber liquid is recovered which solidifies upon standing. The product recrystallized from alcohol melts at 4344 C. Analysis of the 3-cyclohexylthio-3-azabicyclo[3.2.2.]nonane gives 70.08 percent C, 10.69 percent H, 5.89 percent N and 13.32 percent S compared to 70.23 percent C, 10.53 percent H, 5.85 percent N and 13.39 percent S calculated for C H NS.

3-Cyclooctylthio-3-azabicyclo[3.2.21nonane is an amber colored, viscous liquid which when analyzed gives 7 l .24 percent C, 10.76 percent H, 4.85 percent N and 11.87 percent S compared to 71.84 percent C, 10.93 percent H, 5.24 percent N and 1 1.99 percent S calculated for C H NS.

3-Cyclododecylthio-3-azabicyclo[3.2.2]nonane is a cream colored solid which melts at 6062 C. Analysis gives 4.31 percent N and 9.78 percent S compared to 4.33 percent N and 9.91 percent S calculated for C H NS.

The following data illustrate the use of the compounds as inhibitors for premature vulcanization. For the rubber stocks tested and described below, as illustrative of the invention, Mooney scorch times at 121 C. are determined by means of a Mooney plastometer. The time in minutes (i required for the Mooney reading to rise 5 points above the minimum viscosity is recorded. Longer times are indicative of the activity of the inhibitor. Longer times on the Mooney scorch test indicate greater processing safety. Increases in scorch delay of the stock containing the premature vulcanization inhibitor over stock which contains no inhibitor is shown. Curing characteristics of the stocks are determined by the Monsanto Oscillating Disc Rheometer. All stocks are cured at 144 C. to achieve optimum cure which is determined from Rheometer data. 1 the time in minutes for a rise of 2 Rheometer units above the minimum reading, and 2, is the time required to obtain a modulus percent of the maximum. The difference between these two times, t,,,, 1 is indicative of cure rate.

A natural rubber materbatch is compounded as follows:

Ultimate tensile strength, p.s.i 3,720 4, 120 4,190 4, 300

" messing 5 6. The method of claim 1 wherein the accelerating agent is a thiazolesulfenamide.

7. A vulcanizable composition comprising a sulfur-vul- Stocks are prapared by addmg accelerator antldegradam canizable rubber, a sulfur-vulcanizing agent, an organic vulq 'i 'fi P inhibitors to the masterbatch' 5 canization-accelerating agent selected from the group consistprevulcfimzauon mhlblior ls excluded i the control The ing of thiazole accelerators, thiuram sulfide accelerators, alpropemes of the vulcamzates are shown m table dehyde-amine accelerators and quanidine accelerators and an amount effective to inhibit premature vulcanization, a compound of the formula TAB LE I Stock 1 2 3 4 Masterbatch 155. 0 155.0 165.0 155. 0 CH2 N -1,3-di1nethyl-N -phenyl-p-phenylenediamine. 2.0 2.0 2.0

H 0. 5 0. 5 0. 5 5 2 2.0 2.0 2.0 NSCH CH2 n 3-cyclododecy1thio-3-azabicyc1o[3.2.2.] H2

nonane 0.5 0 Mooney scorch at 121 0.: t1 minutes 27. 7 48. O 32. 9 32. 7

Percent increase in scorch delay- 73 19 18 Rheometer at 144 0.:

t 8.2 10. 2 8.5 8. 5 m4. 11. s 11.0 11.0 10.6 wherein n 1s two to nine. 300% modulus 11650 11850 11800 900 5 8. A composition of claim 7 where n is three.

9. A composition of claim 7 wherein n is five.

10. A composition of claim 7 wherein n is nine. 11. A composition of claim 7 wherein the vulcanizing agent The accelerator-inh1bitor combmatlons of this invention is sulfur.

provide cqmpositions h improved storage Stability? For 12. A composition of claim 7 wherein the accelerating agent ample, thlazolesulfenam de accelerators lose activity upon is a hiazolesulfenamide' Storage' However i l i i accelenitois and.005 50 13. A composition of claim 7 wherein the amount of inhibipercent of the stab1l1zer or 1nh1b1tors of thls 1nvent1on after toris from 0.1 to 30 parts per 100 Parts rubber.

Storage Show greater vulcamzanon effecuveness than 14. A composition of claim .7 wherein the rubber is selected equivialemponioils of combination of Siored alone? from the group consisting of natural rubber and styrene-bucombmed lmmedlately prior to use. Usually 1n composmons tadiene rubber mfended use as prevulcamzauon i the 'i 15. A composition of claim 7 containing furnace carbon w1ll comprlse 5 to 95 percent of the compositron by welght, Mack gg g T3 gfi g f i comlp 40 16. An accelerator-inhibitor combination comprised of an i. figi fi' o 8'3;g 2' n z organic vulcanization-accelcrating agent selected from the m l l OPS 4 M compnse 0 Fame 0 e group consisting of thiazole accelerators, thiuram sulfide acrubber.

celerators, aldehyde-amlne accelerators and quanidlne ac- Although themvemlon hasbeenluusuated bytyplcalexamcelerators and a premature vulcanization inhibitor in an gii h g g 1 ,2 fsgzg g sggz iziggggg tfifgggg i sfi amount effective to inhibit premature vulcanization in rubber closure can be made which do not constitute departure from of the formula the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of inhibiting premature vulcanization of a & vulcanizable rubber containing a sulfur-vulcanizing agent and CH an organic vulcanization-accelerating agent selected from the group consisting of thiazole accelerators, thiuram sulfide ac- NSCH CH1) celerators, aldehyde-amine accelerators and quanidine ac- CH2 celerators which comprises incorporating therein in an amount effective to inhibit premature vulcanization a com- H2 pound of the formula M WAWM wherein n is two to nine.

17. The combination of claim 16 wherein n is three.

wherein n is from two to nine. 18. The combination of claim 16 wherein n is five.

2. The method of claim 1 wherein n is three. 19. The combination of claim 16 wherein n is nine. 3. The method of claim 1 wherein n is five. 20. The combination of claim 16 wherein the accelerator is 4. The method of claim I wherein n is nine. a thiazolesulfenamide. 5. The method of claim 1 wherein the vulcanizing agent is 21. The combination of claim 16 wherein the accelerator in sulfur. N-tert-butyl benzothiazolesulfenamide. 

2. The method of claim 1 wherein n is three.
 3. The method of claim 1 wherein n is five.
 4. The method of claim 1 wherein n is nine.
 5. The method of claim 1 wherein the vulcanizing agent is sulfur.
 6. The method of claim 1 wherein the accelerating agent is a thiazolesulfenamide.
 7. A vulcanizable composition comprising a sulfur-vulcanizable rubber, a sulfur-vulcanizing agent, an organic vulcanization-accelerating agent selected from the group consisting of thiazole accelerators, thiuram sulfide accelerators, aldehyde-amine accelerators and guanidine accelerators and an amount effective to inhibit premature vulcanization, a compound of the formula wherein n is two to nine.
 8. A composition of claim 7 where n is three.
 9. A composition of claim 7 wherein n is five.
 10. A composition of claim 7 wherein n is nine.
 11. A composition of claim 7 wherein the vulcanizing agent is sulfur.
 12. A composition of claim 7 wherein the accelerating agent is a thiazolesulfenamide.
 13. A composition of claim 7 wherein the amount of inhibitor is from 0.1 to 3.0 parts per 100 parts rubber.
 14. A composition of claim 7 wherein the rubber is selected from the group consisting of natural rubber and styrene-butadiene rubber.
 15. A composition of claim 7 containing furnace carbon black.
 16. An accelerator-inhibitor combination comprised of an organic vulcanization-accelerating agent selected from the group consisting of thiazole accelerators, thiuram sulfide accelerators, aldehyde-amine accelerators and guanidine accelerators and a premature vulcanization inhibitor in an amount effective to inhibit premature vulcanization in rubber of the formula wherein n is two to nine.
 17. The combination of claim 16 wherein n is three.
 18. The combination of claim 16 wherein n is five.
 19. The combination of claim 16 wherein n is nine.
 20. The combination of claim 16 wherein the accelerator is a thiazolesulfenamide.
 21. The combination of claim 16 wherein the accelerator is N-tert-butyl benzothiazolesulfenamide. 